Development of Trunk Muscle Exercise Machine

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Sumet Heamawatanachai
Sakara Tunsophon
Sirirat Wongprakornkul


Regular exercise is recommended for being healthy and maintain a well-being life. Trunk muscles are one of the most important muscles which are responsible for balancing and stability. Strengthen these muscles help to improve daily activities and prevent back injury. Therefore, we developed the trunk muscle exercise equipment (TMx) and evaluated the usability of the machine. First, the safety of the equipment was analysed including stress and safety factors. Secondly, the spring that attached to the strain gauge load cell was validated. The spring system was adjustable to increase or decrease resistant for exercise training. Finally, the usability of TMx equipment and software were assessed for the trunk muscle workout. From the safety evaluation of the TMx seat, we used an engineering analysis software based on a 100 kg person. The result showed that the seat could support the weight with the maximum stress of 108 MPa and the factor of safety is equal to 2.315. The validation and calibration of the spring system showed that the spring constant value was 3.31 N/mm. The calculation of forces from spring extension and from load cell were close with the difference is not over than 1.7%. Furthermore, the exercise equipment was easily adjusted to the forward and backward modes for trunk muscle exercise. The software was able to determine the force during the exercise workout. In conclusion, the developed machine (TMx) is safe with high validity of the spring-force measurement system. The adjustability of the TMx mode is easy and can be applied for the abdominal and trunk muscle exercises. However, further assessment is required in the large numbers of healthy volunteers in order to elucidate its effectiveness.

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Engineering and Architecture